Remove unused state following removal of a2dp_concurrent_source_sink am: 4f16b745 am: 16dfa137

Original change: https://android-review.googlesource.com/c/platform/packages/modules/Bluetooth/+/3254600



Change-Id: Ia402ee04fcfa9a44172bf1a9ae58f4d664a4a444
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>